1. Field of the Invention
The present invention relates to a syringe (injection syringe) and particularly relates to a prefilled syringe that is already filled with a drug and is capable of injecting a patient at once simply by the fitting of an injection needle.
2. Background Information
Conventional so-called prefilled syringes where a syringe barrel of an injection syringe is filled with a drug in advance are well-known. Such prefilled syringes are equipped with a nozzle for fitting an injection needle at one end of a syringe barrel constituting a body of the syringe. At the other end, an opening is provided where a plunger having a gasket at a tip of a plunger rod can be freely moved backwards and forwards. After filling with a drug, the nozzle is usually covered over with a cap made of rubber in order to prevent leakage of the drug. The entire item is then blister-packed or pillow-packed with the plunger installed. Injection syringes prefilled with a drug where a nozzle covered with a cap is then covered with a heat-shrinkable resin film (shrink film) in order to prevent the cap from coming off as well as in order to prevent the filled drug from being tampered with have also been the subject of applications (for example, Japanese Patent Laid-Open Publication No. 2002-315827). However, when the syringe is made of plastic, it is necessary to store the syringe in barrier packing material having gas barrier properties in order to suppress deterioration of the drug filling the syringe barrel.
If the syringe is stored in a barrier packing material, the drug filling the syringe barrel does not degrade because of the gas barrier properties. However, the prefilled syringes are usually removed from the packaging beforehand in preparation in order to increase operation efficiency at the location of use such as a hospital and enable use at any time. There is, therefore, the problem that the drug will gradually degrade when left without use for a long period of time. When the barrier packaging is unwrapped and the syringe barrels that do not have gas barrier properties are left out, there is the fear of deterioration due to oxidation of the drug filling the barrel. Prefilled syringes provided with labels including inorganic compound deposition plastic film at 70% or more of the outer surface area of the barrel portion of the prefilled syringe have also already been filed (for example, Japanese Patent Laid-Open Publication No. 2004-267662).
Costs are also high when barrier packaging is used or when using barrier packaging in blister packaging or pillow packaging. Enclosure such as silica gel or ageless (registered trademark) (deoxidant) is also necessary in order to remove moisture and oxygen from within the packaging and this also invites high costs.